The present invention relates to artificial human implantable devices. More specifically, the present invention relates to an artificial retinal implant device.
The human visual process is complex and has many aspects that are not yet well understood. However, it is well known that the retina is an essential element for human vision. The present understanding of the physiological process of vision in humans can be summarized as follows.
Light entering the eye is focused by the cornea and lens onto the retina. The retina comprises layers of rods and cones. Additionally, the retina comprises horizontal, bipolar and amacrine cells. Finally, the retina comprises a layer of ganglion (nerve) cells. The light penetrates the relatively transparent outer layer of the retina and is intercepted by the rod and cone cells. In response to the incoming light, the rod and cone cells initiate a neuro-electrochemical reaction. The neuro-electrochemical reaction initiated by the rod and cone cells stimulates the ganglion cells via the bipolar, horizontal and amacrine cells or a subset thereof. The ganglion cells form the terminus of the optic nerve. The optical nerve transmits the neuro-electrochemical signal to the Lateral Geniculate Nucleus (LGN) which then transmits an amplified version of the signal to the brain's occipital lobe. Once the occipital lobe receives the proper stimulation, the brain "sees".
A damaged retina results in the loss of partial or total sight, as the retina is needed to convert the incoming visible light energy into the neuro-electrochemical signal needed by the brain. There are a number of retinal ailments, such as diabetic retinopathy, macular degeneration, retinitis pigmentosa, etc., which partially or completely destroy the retina's ability to intercept light and convert it into a corresponding neuro-electrochemical signal. Therefore, a person with one of the above ailments either partially or entirely loses his or her sight. Unfortunately, there are no known medications or surgical techniques for curing the above ailments and restoring the retina so that it can serve its proper role in the visual process.
As a result, researchers are actively seeking a way in which to create an artificial retina that would serve the function of a real human retina. The artificial retina recently suggested by these researchers is rather bulky as it includes a camera, mounted on eyeglasses, that captures visual images using a charge-coupled device (CCD) sensor. The CCD sensor digitizes the visual images intercepted by the camera. The digital representations of the images are then beamed via laser pulses onto a microchip implanted in the eye. The microchip includes an electrode array and a stimulation circuit. Using the electrode array, the microchip converts the laser pulses into a pattern of electric signals. In theory, these signals would then stimulate the nearest ganglion cells, which would then transmit the information to the brain via the optic nerve, enabling the wearer of the artificial retina to perceive an image.
It is to be noted that the above suggested artificial retina has not yet been developed for human use nor has it been tested on human subjects. The researchers in the area have not yet been able to develop an implantable portion of the artificial retina that can be left in the human eye for an extended period of time without damaging the eye. Moreover, the researchers have put off dealing with the issue of the electrical interface between the device and the brain until the implantable portion of the device is ready for implantation in humans since they believe that optimizing the electrical interface requires feedback from experimental subjects, i.e., human subjects. As there are still key aspects of the proposed artificial retina that have yet to be designed and tested, the suggested artificial retina is far from being reduced to a practical working model.
In addition to not having been reduced to a usable model, the above mentioned artificial retina suffers from several disadvantages. First, the device is too large to be entirely placed inside the eye. This is mostly a result of the use of a camera, which is placed on eyeglasses, to capture the visual images. The bulky nature of the device makes it both heavy and aesthetically unappealing. Second, since the device is not entirely implanted in the eye, it likely will suffer from reliability problems. Additionally, since the device is not entirely placed in the eye, the user of the implant must either continuously wear the eyeglasses with the camera disposed thereon or keep it near by for wearing when needed. When not wearing the eyeglass-camera combination, the user of the artificial retina must have a way of accessing the eyeglass-camera combination without the benefit of normal vision, as the user's vision is at least partially and perhaps totally impaired without the device. Moreover, the eyeglass-camera combination can be misplaced, which may subject the owner to the expense of purchasing a new eyeglass-camera combination. Finally, it may be difficult or impractical to expect the laser beam to reliably remain focused on the implant in the eye.
Therefore, it is desirable to have a retinal implant that is entirely insertable in the eye and overcomes the disadvantages associated with the implant described above.